FR2875712A1 - DEVICE FOR EXTRACTING AT LEAST ONE GAS CONTAINED IN A DRILLING MUD AND ASSOCIATED ANALYSIS ASSEMBLY - Google Patents

Abstract

This device (53) comprises an enclosure (63), means (65) for supplying the drilling mud into the enclosure (63), means (67) for discharging the drilling mud from the enclosure. (63). It further comprises means (69) for introducing a carrier gas into the enclosure (63) and a gas extraction pipe (71) which opens into the enclosure (63), connected to means ( 109) suction. The device (53) further comprises means (72) for selective venting which comprise a vent pipe (115), stitched onto the extraction pipe (71) and sealing means (117) of the vent line (115). These means (117) are suitable for opening the vent pipe (115) when the pressure at at least one point (121) of the device is less than a predetermined set value. Application to the analysis of the gas content of the sludge obtained of an oil well drilling.

Description

The present invention relates to a device for extracting at least one

  gas contained in a drilling mud, of the type comprising:

  - a speaker; means for feeding the drilling mud into the enclosure; means for evacuating the drilling mud from the enclosure; means for introducing a carrier gas into the enclosure; - A gas extraction pipe, opening into the upper part of the chamber and connected downstream of the enclosure, suction means.

  When drilling an oil well or other effluent (in particular gas, steam, water), it is known to perform an analysis of the gaseous compounds contained in the drilling muds emerging from the well. This analysis makes it possible to reconstitute the geological succession of the formations traversed during the drilling and intervenes in the determination of the possibilities of exploitation of the deposits of fluids encountered.

  This analysis, carried out continuously, comprises two main phases. The first phase consists in extracting the gases conveyed by the sludge (for example hydrocarbon compounds, carbon dioxide, hydrogen sulphide). The second phase consists in qualifying and quantifying the extracted gases.

  In the first phase, mechanically agitated degassors of the aforementioned type (US-A-4,635,735) are used frequently. The gases extracted from the sludge, mixed with the carrier gas introduced into the chamber, are conveyed by suction via the gas extraction pipe to an analyzer which allows the quantification of the extracted gases.

  Such devices are not entirely satisfactory. Indeed, the extraction of gases requires a strong agitation of the sludge in the enclosure. Under the effect of this agitation, sludge residues are thrown against the walls of the enclosure, and in some cases clog the pipe through which the carrier gas is introduced into the enclosure.

  Under the effect of suction by the extraction pipe, the pressure in the enclosure decreases. Below a critical value, the sludge is sucked into the extraction pipe and conveyed through this pipe.

  The gas analysis must then be interrupted to replace the extraction pipe and clean the analysis means, if they have been polluted.

  The main purpose of the invention is therefore to increase the reliability of the extraction and analysis of the gases contained in a drilling mud.

  To this end, the invention relates to a device of the aforementioned type, characterized in that it further comprises selective venting means comprising: a vent pipe, stitched on the extraction pipe ; And means for closing the vent pipe, adapted to open this vent pipe when the pressure at at least one predetermined point of the device is less than a predetermined set value.

  The device according to the invention may comprise one or more of the following characteristics, taken separately or in any technically possible combination: said closure means are adapted to open the vent pipe autonomously; the predetermined point is disposed on the vent pipe, between the closure means and the extraction pipe; the closure means comprise a liquid; - The vent pipe comprises a siphon portion, said liquid being disposed in said siphon portion when the pressure at the determined point is greater than said set point; the internal volume of said siphon portion is less than 10% of the internal volume of the chamber; and said means for introducing a carrier gas into the enclosure comprise an air intake at atmospheric pressure, the difference between the setpoint value and the atmospheric pressure being less than 50 mbar.

  The invention further relates to a set of analysis of at least one gas contained in a drilling mud, of the type comprising: - sludge removal means; an extraction device as defined above, the sampling means opening into said means for feeding the sludge; gas analysis means connected to said extraction pipe.

  An exemplary implementation of the invention will now be described with reference to the accompanying drawings, in which: - Figure 1 is a schematic vertical sectional view of a drilling installation, provided with a set of analysis according to the invention; and FIG. 2 is a diagrammatic view, in vertical section, of the main elements of the analysis assembly according to the invention.

  In all that follows, the terms upstream and downstream are related to the direction of flow of a fluid in a pipe.

  An analysis assembly according to the invention is used, for example, in a drilling installation of an oil production well.

  As illustrated in FIG. 1, this installation 11 comprises a drilling pipe 13 in a cavity 14 pierced by a rotary drilling tool, a surface installation 17, and an analysis assembly 19 according to the invention.

  The drilling pipe 13 is disposed in the cavity 14 pierced in the subsoil 21 by the rotary drilling tool. This duct 13 comprises, at the surface 22, a wellhead 23 provided with a discharge pipe 25.

  The drilling tool 15 comprises a drill head 27, a drill string 29, and a liquid injection head 31.

  The drilling head 27 comprises drilling means 33 of the rocks of the subsoil 21. It is mounted on the lower part of the drill string 29 and is positioned in the bottom of the drill pipe 13.

  The liner 29 comprises a set of hollow drill pipes.

  These tubes delimit an internal space 35 which makes it possible to bring a liquid from the surface 22 to the drill head 27. For this purpose, the liquid injection head 31 is screwed onto the upper part of the lining 29.

  The surface installation 17 comprises means 41 for supporting and rotating the drill bit 15, means 43 for injecting the drilling fluid and a vibrating screen 45.

  The injection means 43 are hydraulically connected to the injection head 31 to introduce and circulate a liquid in the internal space 35 of the drill string 29.

  The vibratory screen 45 collects the drilled residue liquid that exits the drain line 25 and separates the liquid from the solid boreholes.

  As illustrated in FIG. 2, the analysis assembly 19 comprises means 51 for sampling the sludge, stitched on the emptying line 25, a device 53 for extracting gas, and means 55 for analyzing the gases. extracts. In a variant, the sampling means 51 are stitched into a liquid receiving tank into which the emptying line 25 opens.

  The sampling means 51 comprise a liquid picking head 57 disposed projecting in the drain line 25, a connecting pipe 59, and a peristaltic pump 61 whose flow rate is adjustable.

  The extraction device 53 comprises an enclosure 63, a conduit 65 for supplying sludge into the enclosure 63, a pipe 67 for evacuating the sludge from the enclosure 63, means 69 for introducing a gas vector in the enclosure 63, a pipe 71 for extracting gases extracted from the chamber 63 and means 72 for selective venting.

  The enclosure 63 comprises a sealed container whose internal volume is for example between 0.04 liter and 0.3 liter. This enclosure 63 comprises a lower part 73, in which the sludge circulates and an upper portion 75 which has a gaseous sky. The chamber 63 is also provided with stirring means 77, comprising an agitator 79, projecting into the chamber 63 and driven in rotation by a motor 81 mounted on the upper part 75 of the enclosure 63. agitator 79 comprises a stirring mobile 83 immersed in the sludge.

  The mud feed pipe 65 extends between the outlet of the peristaltic pump 61 and an inlet opening 85 formed in the lower part 73 of the enclosure 63.

  This feed line 65 may be provided with means for heating the sludge (not shown), in order to bring the temperature of this sludge to values between 25 and 120 ° C., preferably between 60 ° and 90 ° C.

  The evacuation duct 67 extends between an overflow passage 87 formed in the upper part 75 of the enclosure 63 and a retention tank 89 intended to receive the sludge discharged from the device 53.

  Alternatively, the retention tank 89 is formed by the receiving tank 90 of the liquids extracted from the vibrating screen 45.

  The discharge pipe 67 comprises successively an upstream portion 91 inclined downwards, which forms an angle of approximately 45 with the horizontal, a bent portion 93 forming siphon, and a substantially vertical downstream portion 95, open at its lower end 97 disposed opposite the tray 89, above the level of the liquid contained in the tray 89.

  The sludge introduced into the enclosure 63 via the supply line 65 is evacuated by overflow into the evacuation pipe 67 through the overflow passage 87. Furthermore, a portion of the evacuated sludge temporarily resides in the trap 93. of the evacuation pipe 67, which makes it possible to prevent the entry of gas into the upper part 75 of the enclosure 63 through the lower end 97 of the evacuation pipe 67. The introduction of gas into the enclosure 63 is therefore carried out only by means of introducing vector gas 69.

  The sludge collected in the retention tank 89 and in the tank 90 is recycled to the injection means 43 by a sludge recirculation pipe 98.

  The means 69 for introducing a carrier gas into the enclosure include an air intake 98 mounted on the upstream portion 91 of the exhaust pipe 67. This air intake 98 opens into an injection passage 99 on the evacuation pipe.

  In the example illustrated, the carrier gas is constituted by the surrounding air around the installation, at atmospheric pressure, so that the pressure in the chamber 63 is kept substantially constant at atmospheric pressure, when the passage of Injection 99 is opened.

  The extraction pipe 71 extends between an extraction opening 101 formed in the upper part 75 of the enclosure and the analysis means 55. It comprises, from upstream to downstream, an upstream part 103, a liquid recovery pot 104, a volume flow regulator 105, a transport line 107, and suction means 109.

  The recovery pot 104 has a receiving opening into which the upstream portion 103 opens, and in its upper part, an outlet opening connected to the regulator 105.

  In a variant, a filtration stage is interposed between the pot 104 and the regulator 105.

  The pot 104 is provided at its base with a drain line 104A equipped with a valve.

  The flow regulator 105 is formed by a tube having a constriction 106 of calibrated cross-section.

  The transport line 107 connects the enclosure 63, disposed in the vicinity of the wellhead 23, in an explosive zone, to the analysis means 55, disposed away from the wellhead 23, in a non-explosive zone for example in a pressurized cabin.

  This transport line 107 may be made from a polymer material, especially polyethylene, and for example has a length of between 10 m and 500 m.

  The suction means 109 comprise a vacuum pump which allows the suction conveyance of the gases extracted from the chamber 63 to the analysis means 55.

  The means 72 for selective venting comprise a vent pipe 115, and means 117 for closing the vent pipe 115.

  The vent pipe 115 is stitched on the upstream portion 103 of the extraction pipe 71, between the recovery pot 104 and the extraction opening 101.

  It comprises a siphon portion 119 which has two parallel columns 119A and 119B interconnected by their lower ends.

  The right column 119B in FIG. 2 is connected to the extraction pipe 71 by a substantially horizontal pipe segment. The left column 119A in Figure 2 is connected to a vent, which may be the gas surrounding the plant 19, or a reservoir of a neutral gas.

  The sealing means 117 comprise a liquid disposed in the siphon part 119 of the vent pipe 115.

  The liquid disposed in the columns 119A and 119B is constituted by a cleaning liquid, for example water, or by a low-volatility liquid, for example an oil. More generally, this liquid does not generate gaseous compounds capable of interfering with the compounds to be quantified by the analysis means 55, in particular the C 1 to C 8 hydrocarbons and the aromatic compounds such as benzene, toluene and xylene.

  The height of the liquid in the columns 119A and 119B is chosen so that, when the pressure at point 121 of tapping between the vent line 115 and the extraction line 71 is less than a predetermined set value, the liquid in the vent pipe 115 is sucked and flows into the extraction pipe 71.

  The difference between the set point and the atmospheric pressure is between 0 mbar and 50 mbar, in particular between 10 mbar and 40 mbar.

  On the other hand, the internal volume of the columns 119A and 119B is chosen, so that the volume of liquid required to seal the vent line 115 is less than 10% of the internal volume of the enclosure 63. The volume of liquid is also smaller than the volume of the liquid recovery pot 104.

  The left column 119A is provided with a sensor 123 for detecting liquid in the column 119A, electrically connected to means 125 for controlling the assembly 19. When the sensor 123 detects the absence of liquid in the column 119A, it generates an alarm signal which is transmitted to the control means 125.

  The analysis means 55 comprise an instrumentation 131 which allows the detection and quantification of one or more extracted gases.

  This instrumentation 131 comprises, for example, infrared detection apparatus for the quantification of carbon dioxide, FID (flame ionization detector) chromatographs for the detection of hydrocarbons or TCD (thermal conductivity detector), depending on the gases. to analyze. It also comprises a gas chromatography system coupled to a mass spectrometer, this system being designated by the abbreviation GC-MS. The simultaneous detection and quantification of a plurality of gases is therefore possible.

  These means 131 are connected to a tapping on the line 107 located upstream of the vacuum pump 109, in the vicinity of this pump 109.

  The operation of the analysis assembly 19 according to the invention, when drilling a well will now be described as an example, with reference to FIG.

  To perform the drilling, the drilling tool 15 is rotated by the surface installation 41. A drilling fluid is introduced into the interior space 35 of the drill string 29 by the injection means 43. The liquid descends to the drill head 27, and passes into the drill pipe 13 through the drill head 27. This liquid cools and lubricates the drilling means 33. Then, the liquid collects the solid cuttings resulting from the drilling and goes up through the annular space defined between the foaming lining 29 and the walls of the drill pipe 13, and is then discharged through the drain pipe 25.

  With reference to FIG. 2, the peristaltic pump 61 is then activated, in order to collect, in a continuous manner, a determined fraction of the drilling mud circulating in line 25.

  This fraction of sludge is conveyed to the enclosure 63 via the supply line 65.

  The agitator 79 is rotated by the motor 81, and agitates the sludge in the lower part 73 of the enclosure 63 to cause the extraction of the gases contained in this sludge, as well as the mixture of the extracted gases with the carrier gas sucked by the injection passage 99.

  The gaseous mixture is extracted via the extraction pipe 71, under the effect of the suction produced by the vacuum pump 89. This mixture is conveyed to the analysis means 55, where it is qualified and quantified by the instrumentation 131.

  When sludge residues projected on the walls of the enclosure 63 and the evacuation pipe 67 block the injection passage 99, the aspiration of the gaseous mixture from the enclosure 63 by the vacuum pump 109 does not occur. is not compensated by the introduction of carrier gas in the chamber 63. As a result, the pressure in the chamber 63 and in the extraction pipe 71 decreases.

  When the pressure in the extraction pipe 71 decreases below the set point, in particular at the point of sewing 121, the liquid contained in the vent pipe 115 is sucked into the extraction pipe 71.

  When all of this liquid is passed through the extraction line 71, the vent line 115 is disengaged. The liquid is collected in the recovery pot 104. The extraction pipe 71 is connected to the vent, and the value of the pressure in the upstream portion 103 of the pipe 71, then in the chamber 63 goes up almost - immediate at atmospheric pressure.

  Therefore, only the liquid initially contained in the vent pipe 115 is sucked into the extraction pipe 71. As a result, the clogging of this pipe 71 or / and the analysis means 55 by the drilling mud is avoided.

  The sealing means 117 are adapted to open the vent line 115 autonomously when the pressure at the point 121 is lower than the set point.

  The detection sensor 123 then detects the absence of liquid in the left column 119A and transmits an alarm signal to the alarm means 125.

  The injection passage 99 is then cleaned by an operator or an automated cleaning device, and then a predetermined amount of liquid is introduced into the vent line 115 to seal it.

  The analysis assembly 19 is returned to service very quickly, without the need to clean or even replace the extraction line 71, the vacuum pump 109, and / or the instrumentation 131 means of analysis 55.

  In a variant, the sealing means 117 comprise a frangible valve or a valve controlled by pressure.

  In the latter case, the opening of the valve can be controlled when the pressure at a point of the upstream portion 103 is less than the predetermined set value.

  With the extraction device 53 according to the invention, it is possible to have a particularly reliable assembly for extracting and analyzing the gases contained in a drilling mud.

  This device 53 allows, by simple and inexpensive means, to avoid clogging of the extraction pipe 71 by the drilling mud, which increases the productivity and safety of drilling.

Claims (8)

  1. Device (53) for extracting at least one gas contained in a drilling mud, of the type comprising: - an enclosure (63); means (65) for feeding the drilling mud into the enclosure (63); means (67) for evacuating the drilling mud from the enclosure (63); means (69) for introducing a carrier gas into the enclosure (63); - A gas extraction pipe (71) opening into the upper part (75) of the chamber and connected downstream of the chamber (63) to suction means (109); characterized in that it further comprises means (72) for selective venting comprising: une a vent line (115) stitched onto the extraction line (71); And means (117) for closing the vent line (115), adapted to open this vent line (115) when the pressure at at least one predetermined point (121) of the device is less than a value of predetermined setpoint.   2. Device (53) according to claim 1, characterized in that said shutter means (117) are adapted to open the vent pipe (115) independently.   3. Device (53) according to one of claims 1 or 2, characterized in that the predetermined point (121) is disposed on the vent pipe (115) between the closure means (117) and the pipe extraction (71).   4. Device (53) according to any one of the preceding claims, characterized in that the closure means (117) comprise a liquid.   5. Device (53) according to claim 4, characterized in that the vent pipe (115) comprises a siphon portion (119), said liquid being disposed in said siphon portion (119) when the pressure at the determined point (121) is greater than said setpoint.   6. Device (53) according to any one of claims 4 or 5, characterized in that the internal volume of said portion (119) forming siphon is less than 10% of the internal volume of the chamber (63).   7. Device (53) according to any one of the preceding claims, characterized in that said means (67) for introducing a carrier gas into the enclosure comprise a plug (98) of air at atmospheric pressure, the difference between the set point and the atmospheric pressure being less than 50 mbar.   8. Analysis assembly (19) of at least one gas contained in a drilling mud, characterized in that it comprises: - means (51) for sampling drilling mud; - A device (53) according to any one of the preceding claims, the sampling means (51) opening into said supply means (65) of the sludge; gas analysis means (55) connected to said extraction pipe (71).